The incident, in which a mother abandoned her four underage children, took place in 1988 in Tokyo's Toshima-ku. The children's names were never released; they were known as Children A, B, C, D, and E (in Japanese, A-chan, B-chan, C-chan, D-chan and E-chan).
Child A, a boy, was born in 1973; Child B in 1981. Child C died soon after birth in 1984. Children D and E were born in 1985 and 1986 respectively.
All of the children had different fathers. Though it is unclear, it appears that besides Child A, several (perhaps all) of the other children were unregistered. None of the children attended school.
In the autumn of 1987, having met a new boyfriend, the mother placed Child A in charge of the others, leaving him with ¥50,000 (around US$350 at the time) for their living expenses in their Tokyo apartment.
In April 1988, the youngest, Child E, was assaulted by friends of Child A (known only as Friend A and Friend B), and died as a result. On July 17 of the same year, acting on a tip from the landlord, Sugamo officials entered the apartment and discovered the severely malnourished Child A (then 14), Child B (seven), and Child D (three). They also found the body of Child C.
The information given by the children was vague. It was determined that the malnourishment was caused in part by the children's diet, which consisted largely of food bought at convenience stores.
As a result of news coverage of the incident, the mother turned herself in on July 23. Her testimony revealed that the children had been alone for about nine months, and also that the whereabouts of Child E were unknown. On July 25, Child A's testimony revealed that Child E had been killed by a friend of Child A, and that her body was buried in a woods in Chichibu.
In August 1988, the mother was indicted for child abandonment. She received a three-year sentence, suspended for four years. Although Child A was probably not present at the time of his sister's death, he did assist Friend A in burying the body; he was indicted for abandoning a body, but in consideration of the circumstances was remanded to a care facility.
The case bears certain similarities to that of Rie Fujii, a Japanese woman who left her two toddlers alone for ten days in an apartment in Calgary Alberta, Canada, while she visited her boyfriend.
The 2004 film Nobody Knows presents a fictionalized and on the whole less grim account of the affair. In the film, there is no mention of Child C, whose body the mother kept in the family apartment following the child's death. Similarly, rather than being killed by Child A's friends, in the film Child E dies after an accidental fall. Nevertheless, the harsh realities of four young children struggling to survive penniless and alone in Tokyo are documented unflinchingly.
Yūya Yagira won a Best Actor Award at the 2004 Cannes Film Festival for his portrayal of the oldest child.